Jade polishing

Hi,I am trying to reconstruct the polishing technique my grandfather used in the 1960s for jade. He got excellent results and avoided orange peel. I have the original leather laps he used, which range from 3,000 to 100,000 grit. What I haven't been able to determine is what polishing material he used...I assume diamond or carbundum. The laps have a reddish stain on them similar to rouge.

Anyone know how can ascertain this?

FYI, as a child I sat at his side and watched him work, and am now setting up his old equipment...the challenge is figuring out exactly how he did it.

HiI have had some jade that polished easy with no orange peeling and others that I couldn't get a decent polish no matter what I did. One old lapidarist that I knew told me to use a worn out 600 grit belt dry. I have tried this and got good results most of the time. The stone will get quite hot and you have to be careful the stone does not pop off. I have had better luck using the resin bonded diamond sanding disc with water on a hard flat wheel. They are maybe 1/16 thick or less and have less give than the belts on a expanding drum. Diamond is also better because it maintains its cutting edge longer and doesn't round off. The disc are made by several companies such Ameritool and Crystalite. Diamond is more expensive of course but last a long time and more than worth it in time saved and overall cost. They come in grit from 220-8000. When it comes to polishing a lot of people use Chrome oxide on leather but I have never tried it and generally just use Aluminum oxide then diamond paste if you want a higher shine. Jade is one of those stones that usually does what it wants no matter what you do. I hope this helps some.Donald

As a side note...folks with more time spent on this than I suggest that the first step to nephrite jade work is to cut the raw material in three different directions.Then do a polish on the three sides, one direction will be better. The claim is that nephrite morphs the actinolite/asbestos crystal which are more or less laying flat next to each other. So if they are right then one direction you will likely go across or perpendicular to the crystal which does not polish well. In my playing with this it appears to be true. Also since nephrite is a metamorphic material there are always inconsistant results thats why the stuff looks different from different locations. Not unlike a cake mixed and baked at a different temp.

I tend to have best results with diamond. Kind of sounds like your grandfather may have used a red rouge bar to help keep the diamond charge on the lap.

Jade is not that hard to polish with the right tools. and good jade. Not all jade will polish well.

I have made jade cabs, spheres, book ends, and just polished pieces for decades with and without orange peel. I use a Genie starters. When I get to the 600 grit stage, I switch to a wornout 600 grit silicon carbide belt. After that I use a leather or felt buffing wheel at slow speeds with tin oxide and a very light touch. You can get really good results with 3,000 grit diamond paste inplace of the tin oxide.

I just wanted to point out that Chrome Oxide is very, very messy! I've found it works OK on Jade, and serpentine as well, however, its hard to get off your hands and out of your clothes, and I'm not really sure why anybody would want to use it on a non-green jade. I've found alot of reddish rust colored minerals on the skin of river worn Jade and it makes a huge mess when cutting if its a soft rind. Wonder if that could be a source of the red in the leather?

Re: Michael Croxell comment on jade structure. The toughness of nephrite jade is due to the "micro-interfelted" texture of the tremolite/actinolite crystals. There is no directionality to this texture. Sometimes, there are veins of parallel growth tremolite within a piece of nephrite which exhibit chatoyancy, but these are probably not tecnically nephrite themselves. There is a lot of variation in a jade deposit and many associated alteration minerals and inclusions. Talc, asbestos, serpentine, coarser tremolite/actinolite are common associations with the metasomatic process that forms nephrite. Uvarovite and chromite are common inclusions. The relative hardness and size of inclusions can influence the quality of the polish. The grade of the nephrite is related to colour shade and the brightness of the polish it takes. Nephrite is also subject to retrograde metamorphism,where it starts to become serpentinized. High pressures also cause some to be schistose or irregularly micro-fractured. These changes all affect grade, toughness and polishability. The value per pound can vary from a few dollars to around a hundred dollars, depending on quantity purchased. I guess this old jade miner/geologist just got triggered into rambling a bit.

Alex,Ramble on! What areas have you mined jade? Have you ever collected in Washington state? I appreciate your prespective on jade, especially in regards to it's variability. I'm still learning the ropes, but I think I'm past the neophyte stage Have you any interesting examples of jade? Blacks, patterned, botryoidals, reds?It was my understanding that the "orange peel" is caused by the "undercutting" of softer inclusions. It is also my understanding that the difficulty of cutting/polishing jade has been over stated. Traditionally beeswax has been used as a final treatment to jades...perhaps to combat a little left over 'orange peel'?

An old cutter admonished me that approaching the polishing of jade as if it was, say,chalcedony, is a mistake. The secret he said was to go slow and avoid heat. This was brought to mind by the talk in one earlier comment about heat causing the dopping wax to soften and losing the stone...There has been some controversy over whether or not the old theory of the Bielby effect needing heat and pressure to slide the surface molecules into all the fine scratch grooves and smooth the surface into a polish is actually what is going on..but in the case of jade, as Alex mentioned, there are many factors involved and one of them is the variable hardnesses of inclusions and various parts of the metamorphosed mixture that is jade. This is why, I still think that diamond is the answer, since you can get down to extrememly fine lines of abrasion which eventually give way to a good polished surface. Diamond's advantage over carborundum,, is that is maintains its sharpness of cutting and as a result generally cuts away soft and hard at the same rate, and allows surfaces of uneven hardness to attain a smooth finish.

I was asked recently to facett some Cowell Jade,all went well till the polishing stage!.I tried everything but was always left with scratches!,eventually I found that 50,000 diamond spray on a tin lap worked very nicely!,but only with the machine on idle!,very slow,and checking often,no presssure at all,dont even hold it,just pick gently off to check.I learnt a good lesson tho,never offer to cut and polish anything I havent had a good play with beforhand.

Can you put jade in a rock tumbler? Or doesn't it have much effect. I'm about to start working with nephrite jade from NZ for the first time. And I'm a complete novice. So any and all advice will be well received. Thank you. My jade is of the very dark green variety.Shirley

Bielby flow theory is complete horsepucky. Don't take my word for it, look up the melting temperatures of the minerals we're polishing. Things would get very exciting indeed if you came anywhere near that kind of heat.

I've only done two BC jade cabs, they were nice but orange-peeled on me.

Diamond on wooden wheels is said to do the trick. Have a friendly local woodturner turn you some discs, impregnate them with 50k and 100k diamond and experiment. Have yet to get around to trying this myself, alas.

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